In this section we will discuss how to test Scala.js code managed as Full cross project. All names for example subproject name such as fooJVM are taken from cross compile example.

Directory Structure

<project root>
 +- jvm
 |   +- src/main/scala
 |   +- src/test/scala
 +- js
 |   +- src/main/scala
 |   +- src/test/scala
 +- shared
     +- src/main/scala
     +- src/test/scala

Similarly to {shared|js|jvm}/src/main/scala folders that contain your code, there can be also {shared|js|jvm}/src/test/scala folders that would contain your tests. Tests that verify correctness of shared code should go to shared test folder, while tests that check Scala JVM code or Scala.js code only should go to jvm or js test folders respectively. Calling sbt> fooJVM/test will execute all tests residing in shared and jvm folders, thus testing Scala JVM code. Calling sbt> fooJS/test will execute all tests residing in shared and js folders, so Scala.js code is tested. In case of the full cross project, root project aggregates JVM and JS parts, so when calling sbt> test will effectively run both fooJVM/test and fooJS/test.

Integration testing

Configuring a regular non-Scala.js sbt project to have it:test is documented in sbt. For a Scala.js project, you will also need to install the Scala.js-specific settings and tasks to the it configuration, as follows:

lazy val myProject = project.in(file(".")).
  enablePlugins(ScalaJSPlugin).
  // add the `it` configuration
  configs(IntegrationTest).
  // add `it` tasks
  settings(Defaults.itSettings: _*).
  // add Scala.js-specific settings and tasks to the `it` configuration
  settings(inConfig(IntegrationTest)(ScalaJSPlugin.testConfigSettings): _*).
  ...

For a crossProject, you also need to setup the shared/src/it/scala source directory. The complete setup is as follows:

lazy val cross = crossProject.in(file(".")).
  // add the `it` configuration
  configs(IntegrationTest).
  // add `it` tasks
  settings(Defaults.itSettings: _*).
  // add Scala.js-specific settings and tasks to the `it` configuration
  jsSettings(inConfig(IntegrationTest)(ScalaJSPlugin.testConfigSettings): _*).
  // add the `shared` folder to source directories
  settings(
    unmanagedSourceDirectories in IntegrationTest ++=
      CrossType.Full.sharedSrcDir(baseDirectory.value, "it").toSeq
  ).
  ...

Now you can put tests in {shared|jvm|js}/src/it/scala and they will run when you call sbt> it:test. Similarly to test, there is also two iterations and they can be executed separately by explicitely stating jvm or js project name, for example sbt> fooJS/it:test.

Testing frameworks

A list of testing frameworks compatible with Scala.js can be found here.

Note: Don’t forget to mark a test framework SBT dependency as test,it if you have both unit and integration tests.

Testing over fullLinkJS-generated files

By default, tests run over fastLinkJS-built (resp. fastOptJS up to Scala.js 1.2.x) JS files since their build time is shorter than fullLinkJS (resp. fullOptJS).

If you want to run tests over fullLinkJS-build JS files for some reason, run set scalaJSStage in Global := FullOptStage before test. This increases test time significantly, and omit checks for undefined behavior, so not recommended in default build settings. Instead, consider run test both in FastOptStage and FullOptStage in CI.